Uncertainty over the hydropower project, which accounts for 60 percent of Ch Karnchang's construction projects in value terms, capped the stock price this year.

It has risen 23 percent so far in 2012, underperforming other builders such as Sino-Thai Engineering and Construction Pcl which has gained 78 percent.

"The project approval is positive and will have a significant impact on Ch Karnchang's fundamentals. We are looking to upgrade earnings forecast and its price target to take into account the Xayaburi project," broker DBS Vickers Securities said in a report.

"Third-quarter sales revenue turns softer, up 14.3 percent YoY but down 1 percent QoQ possibly due to weak food price inflation witnessed in the first half rather than weak sales volume growth," Citigroup said in a report.